Credit: NASA/JPL-Caltech/IPAC/Event Horizon Telescope Collaboration

This image from NASA's Spitzer Space Telescope shows the elliptical galaxy Messier 87 (M87), the home galaxy of the supermassive black hole recently imaged by the Event Horizon Telescope (EHT). Spitzer's infrared view shows a faint trace of a jet of material spewing to the right of the galaxy - a feature that was previously one key indicator that a supermassive black hole lived at the galaxy's center.

More prominent in the image is the shockwave created by that jet. The inset in the image below shows a close-up view of the shockwave on the right side of the galaxy, as well as the shockwave from a second jet traveling to the left of the galaxy.

Located about 55 million light-years from Earth, M87 has been a subject of astronomical study for more than 100 years and has been imaged by many NASA observatories, including the Hubble Space Telescope, the Chandra X-ray Observatory and NuSTAR. In 1918, astronomer Heber Curtis first noticed "a curious straight ray" extending from the galaxy's center. This bright jet (which appears to extend to the right of the galaxy) is visible in multiple wavelengths of light, from radio waves through X-rays. The jet is produced by a disk of material spinning rapidly around the black hole, and spewing in opposite directions away from the galaxy. When the particles in the jet impact the interstellar medium (the sparse material filling the space between stars in M87), they create a shockwave that radiates in infrared and radio wavelengths of light, but not visible light.

The jet on the right is traveling almost directly toward Earth, and its brightness is amplified due to its high speed in our direction. But the jet's trajectory is just slightly offset from our line of sight with the galaxy, so we can still see some of the length of the jet. The shockwave begins around the point where the jet appears to curve down, highlighting the regions where the fast-moving particles are colliding with gas in the galaxy and slowing down.

There is also a second jet on the left that is moving so rapidly away from us it is rendered invisible at all wavelengths. But the shockwave it creates in the interstellar medium can still be seen here. In the Spitzer image, the shockwave is on the left side of the galaxy and looks like an inverted letter "C."

This image from NASA's Spitzer Space Telescope shows M87 looks like a hazy, blue space-puff. At the galaxy's center is a supermassive black hole that spews two jets of material out into space. This image shows a wide-field image of M87, also taken by NASA's Spitzer Space Telescope. The top inset shows a close-up of two shockwaves, created by a jet emanating from the galaxy's supermassive black hole. The Event Horizon Telescope recently took a close-up image of the silhouette of that black hole, shown in the second inset.

Scientists are still striving for a solid theoretical understanding of how inflowing gas around black holes creates outflowing jets.

Infrared light at wavelengths of 3.4 and 4.5 microns are rendered in blue and green, showing the distribution of stars, while dust features that glow brightly at 8.0 microns are shown in red.

The Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Space operations are based at Lockheed Martin Space Systems in Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.